This invention relates generally to apparatus and method for defrosting the evaporator coil of a heat exchange system and, more particularly, to assuring that a defrost action of this coil is timely initiated by the heat exchange system.
The defrosting of the evaporator coil in a heat exchange system will quite often depend on the status of one or more compressors in the heat exchange system. In this regard, defrosting of this coil will usually not take place unless at least one compressor in the system has been on for a minimum period of time. This minimum period of compressor on time assures that the compressor or compressors of the heat exchange system will not be unnecessarily loaded with a defrost when these compressors have only been on for a relatively short period of time. Such a limitation on initiating defrost may however allow for a build up of frost on the evaporator coil during each relatively short period of on time under certain circumstances. In this regard, each time the compressor is turned on, the outdoor coil will possibly collect some condensation, depending on the outdoor weather conditions. If the compressor then turns off shortly after this condensation forms, it will cause some frost to build up. If the unit continues to keep doing this, each short on and off cycle of the compressor will add a little more frost until a point is reached where the frost build up becomes significant.